Lettuce pack and method of packing lettuce



June 4, 1940; E. H. SPIEGL 2,203,033

LETTUCE PACK AND METHOD oF PACKINQLETTUCF Filed Dec. 19, 1958 .ATTORNEYPatented June 4, 1940 UNITED. STATES PATENT OFFICE LETTUCE PACK ANDMETHOD OF Claims.

ing of lettuce for shipment, all of the steps are very carefullycontrolled so that the lettuce harvested from the field will-bepresented to the market in the best possible condition, not only insofaras its inherent value is concerned but also insofar as its appearance isconcerned since lettuce heads which can be made to arrive onthe marketin good physical condition, and especially with a highly attractive,fresh appearance, command a considerable premium over the usual marketprice. It is therefore of immediate commercial value in any wisetoimprove upon the technique or apparatus, involved in the handling oflettuce between the growing eld and ultimate presentation on the market.This' usually involves a great deal of care betweentheactual removal ofthe lettuce from the growing field up to the time it is packaged andshipped-which time is usually within a very few hours of the same day.The shipment time, however, often extends over a number of days sincethe lettuce customarily is shipped the majority of the way or entirelyacross the continent, so that often, despite extra care` exerted by thepicker and the packer of the produce, the conditions of transit are suchas to negative the otherwise beneficial results to be obtained. vTheuniversal practice at the present time, so far as I am aware, is to packthe lettuceheads, after stripping Ithe outside leaves and trimming thestem, into rectangular shipping crates made up of a number of spacedwooden slats secured together. Into the container so formed, a lining ofparafned paper is placed and the heads of lettuce are'then introducedalong with a quantity of crushed ice.

After the maximum number of lettuce .heads have been placed in thecrate, a final charge of crushed ice is heaped upon the top, the ends ofthe waxed paper are folded over on top of the heaped crushedice, and aspringy, resilient, slatted wooden lid is by pressure finally nailed inposition. The bulged crate, along with many others like it, is put intoa refrigerator car until the car isv approximately three-quarters full,crushed ice is then blown into the car on top of the entire load, andthe car is sealed and sent to its destination. Hundreds of thousands ofcars of lettuce areshipped in this way each year,

Upon arrival at destination it is found that a certain number of thepackages of lettuce yare not in good order, for the reason that some ofthe heads have been mechanically squeezed l against the sharp Iedges ofthe crate slats, due 5 to the initial pressure of the resilient lidexerted through the crushed ice, and the heads have been squeezed intoor against the slatted sides of the crates and into the corners thereof,so that material mechanical injury follows. 'Ihis mel0 chanical injuryis particularly apparent upon the heads which have been forced into thecrate corners and against the sharp edges of the crate slats. Thepressure when the crates are initially packed -is large since, tocompensate at 15 least partially for ice meltage within the crate duringshipment, the crate is customarily greatly overbuilt with ice so thatwhen the lid is nailed on deformation and bruising of the heads ensue.Bruising of the leaves is-followed by a milky 20 exudation whichoxidizes red and ruins the appearance of the produce. For resale,therefore, all the outer bruised leaves must be stripped off, thusreducing the head size so much as greatly to lower the retail price, orto make the head un- 25 salablysmall. This retail loss is of the natureof 25% of the crate but heretofore has not been overcome.

There is also mechanical injury to the crates themselves amounting toabout 2% to 5%, im- 30 portant in that recoopering is required anddamage claims against the carrier arise. This v condition is aggravatedby the soaking the crate wood gets from the ice melt so that repair isdiicult or impossible and further use of the 35 crate is impossible.

But the chief economic loss probably arises from the inability todisplay or keep thelettuce for very long after its arrival on the retail ,market That which is not` immediately sold may keep for anotherdays display or it may have deteriorated so badly that it must bediscarded. The addition of each days keeping time is of tremendousvalue. But the keeping 45 time depends largely upon, how soonafterpicking the field heat in the lettuce head can be extracted. Evenwith ice in the crate, the lettuce in the customary paper-lined woodencrate requires from twenty-four to fortyf-eight hoursl 50 injury to thelettuce in packing and in shipment Y will b e materially reduced.

' an improved lettuce'pack which can be shipped with greater 'facilityand with' at least equal ease of handling from the standpoint of size.contourv and weight, as compared with the present package.

A further object of my invention is in general to improve aA lettucepack and the method of packing lettuce. l

The foregoing and other objects are attained in the embodiment of theinvention illustrated in the drawing, in which- Fig. 1 is a longitudinalcross-section on a vertical piane, of a diagrammatically illustratedrefrigerator car packed in accordance with my inv vention;

Fig. 2 is a cross-section the plane of which is indicated by the line2'-2 of Fig. 1; f

Fig. l3 is a cross-section on a diametral. vertical plane, of a lettucepack in accordance with my invention; andl Y' Fig. 4 is a cross-sectionthe plane of which is indicated by the-line l-I of Fig. 3. Y In itspreferred form, the lettuce pack of my invention includes a circularcylindrical container, substantially airand water-tight and 4fabricatedof material having high thermal conductivity, within which aresymmetrically ar-.`

ranged a plurality of heads of lettuce, the majority-of the heads beingin immediate contact with the material of the container and under s.some circumstances being interspersed with crushedwatereice,there'being'a closure means for maintaining the heads of lettuce inposition within the container. The method includes arranging the-headsof lettuce in a predetermined form, confining them to such formsometimes in the presence .of a refrigerant and in the subystantialabsence of air by a means having a high thermal conductivity, andiinaily extracting the eldheat from the lettuce rapidly through a conning means.

In following out lthe conduct of I my inven--I tion, from which both thenew pack and theV method willnappearl I shall dcribe-.the par- 60ticular manner of practicing it -which has resulted in securing apremium over the marketl price. In this instance I have taken acontainer G which is fabricatedA preferably of a vmaterial having arelatively high thermal conductivity, such as sheet iron or steel,coated with aV suitable material inside and outside to precludedeterioration or undesired chemical action in connection with thecontents. The precise thermal ccnductivity of the material isnotcritical. but I have found that metal has a relatively high conductivitywith respect tothe field heat within the\ lettuce, as contrasting withthe relatively low thermal conductivity of the wooden containers atlpresent universally used, particularly when such. containers are linedwith one or more bruising or other damage.

layers of waxed paper, in which event it is very.

diicult for eld heat within the lettuce to be transferred to arefrigerant which surrounds the package as a whole.

In the present instance, the container 6 is preferably a right circularcylinder having in one embodiment a diameter of substantially eighteenand one-quarter inchesand a height of approximately twelve and one-halfinches. The container has a similar metal bottom 1 which is secured byany 4suitable inter-folding 8 with the side walls 9, so that thecontainer is water-tight. A: container 6 of about the indicated size andproportions is `readi1y handled by an operator since its weight is notfar different from that of the present wooden crate and since it canreadil be put on a present packing stand. r 1

When a container is so positioned, lettuce heads 4which have beenltrimmed are arranged on the bottom 1 in a predetermined vand preferablysymmetrical geometrical order, as clearly disclosed in Figs. 3 and 4.vIn this way each of the lettuce heads Il is in direct and immediatethermal conducting relationship with the walls 1 .and 9, yet there areno sharp edges or corners to groove or bruise the produce. Since thecon-- tiner is round and the lettuce head is of similar curvature,whatever pressure there is between them is exerted over alarge area ofcontact, so that the unit pressurejis so low as to obviate The largearea o f contact is also veryfavorable for thermal transfer. Thiscondition is further assisted since the metal walls 6 of the containerare quite thin and are somewhat deformable so that when a layer oflettuce is packed, the .container cross-section can '1 form so that thecontainer wall yields to provide uniform pressure instead of locallypressing upon and bruising the lettuceg In the arrangement .sho'wn'especially in Fig. 4, most of the ten headsV oflettuce in the bottomlayer are in immediate depart from circular into a partially polygonal lthermal contact withthe sides 9 as well aswith the bottom 1, and theremaining central heads are in good thermalcontact with the bottom 1,

vso that a' majority ofthe heads of lettuce in the lower layer areindirect and immediate thermall Of course, the numcontact with thecontainer. ber of heads of lettuce in a'particular layer, .and

the arrangement of the layer, will vary notcnly f with the size of the.heads of lettuce but 'with the diameter of the container; but thearrangement shown is calculated to result in a standard number of headsof lettuce inmy new container.

The-plurality of lettuce heads il in immediate contact with the bottom 1constitute the lower layer, generally designated I2. At this point twovalternatives are possible. 'I'he pack may be inelusive 'of water-ice,termed a "wet pack, or ice -V may bev omitted, resulting in a' dry pack.To -make the wet pack, upon nishing the lower layer l2, the packerintroduces al charge .of crushedV water-ice into the container.

Thev

water-ice spreads itself over the heads of lettuce and lls theinterstices therebetween, vso that an adequate bed is made for thereception of a superposed, .intermediate layer Il constituting. a'notherplurality of lettuce heads I6 which are arranged either in the samegeometrical pattern as was the layerv II or in' a variation thereof',delpending somewhat upon 'the fancy of the packer, Y

butin any case a majority of the heads are in immediate contact with thewall 'I'he layer A I4 is in turn subjected to-a charge ofcrushedwater-ice and `upon it is superposed a top layer I1 on which an icecharge is placed, substantially filling the container.

This procedure may be varied, if desired, by first completely fillingthe container with layers of heads of lettuce and finally charging thecontainer with crushed water-ice in a quantity suf- Iicient to 'fill allof the interstices and also the container. In this instance the heads oflettuce will be in immediate contact with each other rather than spacedby layers of water-icc. In either event the top layer I1 of heads oflettuce is just below the rim I9 of the container 6, and a Iinal chargeof refrigerant in the form of crushed water-ice is introduced.

To follow the dry pack alternative, the heads of lettuce are arranged asdescribed but no ice is added to the container. For a given sizecontainer preferably larger heads are used with the dry pack so that areasonably firmly filled packl age results.

With either the wet pack or the dry pack, when the container is full, aclosure 2|, preferably of metal comparable to that of the sides 9, isengaged with the rim I9 and is effective to retain the contents inposition. The closure 2I can be frictionally retained, can be lightlycrimped in place, as shown in Fig. 3, can be tack welded in position, orcan be otherwise secured. The metal closure is put on the container atsubstantially room temperature 'and before the interior ice, if used,has had much opportunity to reducel the temperature. But subsequently,as the temperature of the closed package and contents is reduced, themetal is contracted, as is the contained air, so that the closure issubsequently removable only with some diiculty. I have found thatpractically the package is substantially water-tight and, although nothermetically sealed, is nearly airtight. Of c'ourse, the package can besealed, and evacuated of air, or can be charged with an inert gas, butthis renement is not ordinarily necessary.

The practical exclusion of air or air circulation is commerciallyeffective greatly to reduce or prevent redness of the lettuce, whichrednessv is- .very undesirable. What oxygen is trapped in the containeris converted into carbon-dioxide by a slight reaction with the lettuce,after which oxidation practically ceases. Whenever a lettuce leaf isbruised and where the lettuce butt' the container and the closure 2l isput on, either dimensions of the car.

by hand or by machine, the container 6 is placed within its shippingcompartment, such as the load compartment of a refrigerator car 23. Thearrangement of the container 6 and a plurality of its fellows within thecar will vary somewhat with the size of the container and the interior Atypical arrangement is illustrated, in which the containers are disposedin rows and files and in superposed layers virtually to the capacity ofthe car, following which interior bridging or bracing 24 is utilized toretain the containers in position, and the interior of the car ischarged with crushed waterice 26 which not only lls the intersticesbetween the adjacent containers 6 but is introduced in suiliicentquantity to form a blanket over the top of the load. This refrigerant isintroduced with the customary ice-slingers now utilized to blow crushedice into the interior vof cars.

'I'he car so iced is then ready for shipment, but the result ensuing ismaterially different from vthat following the use of standard woodencrates with waxed paper lining. In accordance with my invention, thefield heat of the lettuce heads II which are in intimate thermal contactwith the highly conductive walls of the container 6 is dissipated fromthe heads of lettuce directly through the Walls of the container to thesurrounding crushed ice 26. Hence extraction of the eld heat results in`a large melt of the external crushed ice 26 which virtually surroundseach container and can be replaced if necessary, rather than in a rapidmelt of interior ice as occurs with wooden crates. Otherwise stated,whereas with wooden crates the crushed ice contained within the packagemelts very rapidly in extracting the eld heat from the lettuce anddischarges indiscriminately from the package during shipment and evenafter unloading, in the disclosed dry pack arrangement there is nointerior melt, with the wet pack the melt within the package isrelatively slow, and with both of my packs the melt of ice in the car isrelatively rapid. Under comparable practical conditions the ice meltlwithin a crate is at least fifty percent, giving rise to large initialoverbuilding in an endeavor to compensate for it in advance, whereaswith my arrangement the internal melt, where interior ice is used, isnot over ten to fifteen percent. While the external, car melt is muchgreater, the ice can, if necessary, be easily replenished. When thecontainers 6 are finally taken from the car at the end of the journey,the contained lettuce is in good condition, and with the wet pack thereis considerable crushed ice remaining for further refrigerationandpreservation of the lettuce heads when the package is placed on displayin a retail store. Whatever melt occurs from the contained ice I3 does.not escape from the package but remains as cold water in contact withthe lettuce, helping to prevent access of air thereto even though theclosure is not completely air-tight or has been removed, and preventingdesiccation of the lettuce heads. With the dry pack the heads are cold,dry, fresh in appearance and ready for immediate sale.

When the container contents are to be inspected either within the car orat a market, removal of the closure 2| is reasonably easy and exposesimmediately one-third of the lettuce' heads, while removal of the centerheads 22 and 23 exposes all of the remaining heads in the container.Replacement of those heads removed, if any, and of the closure leavesthe package in substantially its original condition before inspection.'I'his contrasts with the crate, the wood of which becomes water-soakedduring several days` subjection to ice melt'and if opened for inspectioncannot be repacked and recoopered to be accepted as anything butrehandled merchandise of greatly lowered value.

This inspection feature is'valuable to the retailer, since he may placethe opened but watertight container directly upon his display stand andexpose the produce while it is still in contact with the the remainingrefrigerant, if any, the melt from which is confined to the containerfone-half of a crate. It vis, therefore possible,v

where space is at a premium, to display.` the original package insteadof unpacking part of the contents from time to time. Half-crates are notfeasible since thereare twicelas many corners' as with a wh'oe crate andhence twice as many opportunities for bruised and damaged heads so thatthe percentage of first-grade heads uneconomically reduced.

Finally, after the lettuce heads have been re"- moved from thecontainer, the container either is reusable under the same circumstancesor has a salvage value for other purposes. The weight of the package andthe ability to handle it are substantially comparable with the presentwooden crate, but the ability to retain the melted ice, if any, butespecially to conduct the field heat of the lettuce rapidly through thematerial of the container, vamong other attributes, has resulted inmaking the dry pack feasible and in reducing the interior icing so thatthe heads of lettuce arrive at the market in so much better than usualstate that a premium is obtainable.

The example described herein has illustrated zine use of water-ice asthe internal and the exernal refrigerant, but other refrigerants, suchas solid carbon-dioxide, are usuable. If Aprecooling facilities areavailable, it is entirely feasible to pack the lettuce heads dry andthen to precool the containers` and contentsprior to loading them intocars. The car cooling utilized after loading 'may involve placing icearound and on the loaded containers or may involve simply thecirculation of chilled air. n

Furthermore, while the example speaks particularly of lettuce and ispeculiarlyI adapted to meet theproblems involved in the marketing oflettuce, it is also usable and beneficial in connection with carrots,peas, artichokes, cauliflower, broccoli andcomparable produce.

claim:

1. A lettuce pack comprising a circular-cylhidr- Y ment' with materialhaving a high thermal con- I ductivity, introducing ice into confinementwith said heads of 1ettuce,and then subjectingsaid heads of lettuce andsaid ice to a rapid extraction of field heat from' said heads of lettucethrough said material.

' 3. A lettuce pack comprising a substantially watertight containerfabricated of material having a high thermal conductivity, a pluralityof Aheads of lettuce packed in layers within and in thermal contact withsaid container, crushed water-ice within said container inheat-transferring relationship with said lettuce heads, and a removableclosure for said container.

4. A lettuce pack comprising a-metal container capable of retainingwater, a plurality of heads of lettuce packed in layers within and inthermal contact with said container, and crushed water-ice within saidcontainerv in heat-transferring relationship with said lettuce heads'.

5. A lettuce pack comprising a metal container, a plurality of heads oflettucefpacked in layers within and in thermal contact with saidcontainer, and crushed water-ice exteriorly of and in heat-transferringrelationship with said container. 1

. ELLIS H. SPIEGL.

